Purification of crude anthracene



UNITED STATES.

PATENT. ornca.

EMIL PORTHEII, OF PRAGUE, REPUBLIC OF CZEGHO-SLOVAKIA,

ASSIGNOB TO THE I FIRM 0F KINZLBERGER G CO., OF SMICHOV-PRAGUE, CZECIIO-SLOVAKIA REPUBLIC.

PURIFICATION OF CBUDE ANTHRACENE.

To all whom it may concern:

B it known that I, EMIL PORTHEIM, manufacturer, a citizen of the Czecho-slovakla Republic, residing at 38 F erdmandsgasse, Prague, in the Republic of Czecho-Slovalna, have invented certain new and useful I mprovements in a rocess for the Purification of Crude Anthracene, of which the followin is a specification.

The known processes for freeing crude anthracene from carbazole by means of potassium hydrate, are discussed fully in German Patent No. 178,764 and there is opposed to the earlier processes as the most advantageous that based on the fusion of crude anthracene with caustic potash and the subsequent distilling oil" of the anthracene in a vacuum. I

All these processes, including the process of German Patent No. 178,764, have in common the employment of high temperatures. German Patent No. 111,359 recommends the temperature of 260 degrees 0.; in the process of German Patent No. 178,764 the anthracene is distilled off from the carbazolepotash melt in a vacuum, which likewise requires a temperature of far above 200 degrees C. Beilstein, vol. IV, p. 390 gives the temperature at which carbazole potassium forms from carbazole and potassium hydrate as 220 to 240 degrees C.

In face of these statements, the invention has for its basis the discovery that the theoretical yield of carbazole potassium from carbazole and potassium hydrate can be ob tained at much lower temperatures, if the carbazole be mixed with potassium hydrate in the presence of a solvent for carbazole and anthracene, for example' hydrocarbons, and boiling until carbazole potassium is formed, water being meanwhile distilled off. In this manner it is possible to produce carbazole potassium even at the boiling point of toluol. On the basis of this discovery, the carbazole can be separated from the crude anthracene in the theoretical quantity.

By employing the-low temperature, it is possible to avoid the losses which are unavoidable when working according to the processes of the above mentioned patent.

The water formed in the aforesaid reaction may be advantageously distilled off mixed with the solvent or larger quantities of caustic potash may be employed, in which Specification of Letters Patent.

.Patented Jan. 17, 1922.

' Application filed August 17, 1920. Serial No. 404,145.

1st example: Crude anthracene, containa ing 53.4 per cent of anthracene is purifiedby dissolving it in na htha of a boiling point of 145 degrees. emi-purified anthracene containing 70 per cent of anthracene is obtained.

10 0 parts by weight of this substance, containlng 70 parts of anthracene are boiled Wlth 30 parts by weight of 75 per cent strength powdered caustic potash and 300 parts by weight of naphtha of a boiling point of 145 degrees, and simultaneously stirred, the boiling being continued so long as water mixed with naphtha passes over; If required the naphtha distilled off must be replaced by introducing fresh naphtha, in order that the anthracene shall certainly remain in solution. The carbazole-potassium separates gradually as a heavy sandy precipitate. When the reaction is complete, the hot anthracene solution is drawn off and after cooling there is obtained an anthracene which when drawn off and separated from the naphtha has a degree of purity far above 90 per cent and contains no trace of carbazole. The carbazole-potassium is freed from the naphtha by means of steam and simultaneously decomposed into carbazole and potassium hydrate. In this manner it is possible, at temperatures which can be easily reached by indirect steam heating, to separate from each other and obtain anthracene and carbazole in most without loss of purity.

If in the above Example 1, the amount of caustlc potash is doubled, complete separat1on of anthracene and carbazole is obtained under the reflux condenser and even at temperatures below the boiling point of the solvent employed. It is however possible to effect the separation in employing the quantity of caustic potash given in the example and using the reflux condenser, but in this case a much longer period of time is necessary to cause the caustic potash to react in a sufficient degree.

Example 2: 150 parts by weight of crude anthracene containing about 50 per cent of anthracene are dissolved bymeans of coal tar naphtha of a boiling point of 130 degrees C., and the paste obtained which cona very simple manner, aland of an excellent degree tains about 70 per cent of pure anthracene, is heated to 120 degrees C. with 200 to 300 part by weight ofnaphtha and 60 arts by weight of 80 per cent caustic potash i the mixture being meanwhile well'stirred.

The further treatment takes place as described in Example 1. The anthracene is.

free from carbazole, and the carbazole is free from anthracene. What I claim is:

1. A process for the separation'of anthracene and carbazole consisting in dissolving the mixture in a neutral solvent, adding caustic potash, and removing the water produced during the reaction in order to avoid decomposition of the carbazole-potassium.

2. A. process for the separation of anthracene and carbazole consisting'in dissolving the mixture in a neutral solvent, adding or some hours,

caustic otash and removing the water pro- 20 I signature in presence of two witnesses. Y

EMIL liORTHEIM; Witnesses:

J. E. CALmHAN, RYDER Fos. 

